You can get Win 10 from your existing 256  GB mSATA onto your new 512 GB  mSATA by imaging all the partitions on the 256 GB drive and then restoring them to the 512 GB drive. You could store the images on your 1 TB SSD. The tool to use is Macrium Reflect Free Edition to image the 256 GB drive. Then using Macrium you also create Rescue Media onto a bootable USB, install the 512 GB drive, then boot the Rescue Media and restore the images to the new drive. Be sure to image all the partitions (Recovery (there may be more than one), EFI, & OS) and restore the partitions one at a time (in the same order, look at the drive with Disk Management) and when you restore the OS partition expand it on the target drive to use the additional space. Download the Macrium Reflect user guide and see the chapter on Backup, imaging, and cloning.
i7-479016GB Ram2TB HD3TB HDD256 Samsung 850 mSATA What I'm hoping to accomplish is to have the OS on 1 SSD (the mSATA port so that I can max out the amount of drives I can put in this computer) and another one to be used as a 'Scratch Disc' (for doing edits, ie. photoshop, lightroom & a bazillion other programs & presets she has). I had a guy set it up for me with the components listed above but my wife didn't use the drives in a manner she needed to (stored some photos on the SSD & filled it to max. capacity... & actually filled all of the drives to max although they are now ~ 1/2 filled.... she also has ~15TB of space on external drives).  She never had it working close to how I'd hoped to have it run for her.... I wanted it to ZOOM!   (fwiw, I didn't even know what was happening with her computer at the time but do now as I just recently took a look at it   ) More 'new' upgrades: 512 GB mSATA Kingston SSD1TB Samsung 860 EVO SSD6TB WD Black HDDGPU:  Zotac GTX 1650 4GB  (Installed & running now, picked this one up due to low wattage requirement, Very small and fits in the DELL perfectly and also to help with the editing while using a 32i" 4K BenQ monitor (which is still in the box since last Christmas due to the DELL not working optimally)32GB Ram (4x 8GB DDR3 1600) installed and running nowCase fan:  Noctua NF-A9 92mm (also have a 120mm Silent Series R2 Fractal I may add later inside the front of case) I have Win10 on the mSATA SSD (moved from the original 32GB ssd that it came with by a tech guy I paid when I first attempted to upgrade her tower a couple yrs. ago.  I'm not 100% sure he even used the Win10 she already had in there as he wasn't interested in taking down any links I gave him for moving the Win that the Dell originally came with as I'd read there were a few things one needed to do to make this happen (I'm not computer savvy at all... can you tell yet?).  I do have another brand new (unused) win10 PRO that I purchased for my wife's mother's computer but she never ended up using it. (maybe I should use it?). I'm wanting to either transfer Win10 from the 256 mSATA SSD to the new 512GB mSATA SSD.  How do I do this? (do I need to move it to another HDD and then install the new mSATA SSD and transfer stuff from the HDD to the new mSATA SSD?).  fwiw, I don't know how to install my new Win10 PRO as I have a 'product key' for it and not a disc. At my disposal I also have the following: 2x 3.0 SanDisk  flash drives (32GB & 64GB) UGREEN External HD Enclosure Adapter 3.5 USB 3.0 to SATA HD Case Housing with Power Adapter for 3.5/2.5" Sandisk, WD, Toshiba, Samsung, Hitachi SATA III, HDD, SSD Sabrent 2.5" SATA to USB 3.0 External HD Enclosure (Optimized for SSD, Support UASP SATA III) and another functioning tower (mine) with tons of space inside (will hold many HD's but a single 250GB SSD is all I need for what I use it for). I'm looking for help.  If someone could give me some thoughts/ideas of how to go about the final stages of getting my wife's Photo Editing Beast up & running 'optimally' I (we) would really appreciate it.  I've tried a couple different puter tech guys in our area and both left me feeling very disappointed.  Why have I taken soooo long to finish this for my wife?  We've had a very rough past couple years with many deaths in our families (we both lost a brother, we both lost our mothers, she also lost her father and most recently we lost our daughter ).  A great Christmas present this year would be to get the previous 'years' presents functioning properly. One thing I know that I did do correctly was the acquisition of parts for upgrading her DELL XPS 8700 and I was able to get most of my ideas/info. from the people here in this forum    So... thanks again for that!
XPS 8700, upgrades to be a Photo Editing beast for my wife