You are looking for NVME SSDs 2280   :  Such as this  Make a note that you don't have to remove your current HDD, unless you are looking for an external HDD only.  2 I want to install ubuntu in SSD. Do i need to change any bios settings to detect bootable SSD? IN BIOS : SATA mode should be changed to AHCI from RAID, & disable secure boot.   2 After installing ubuntu, can i use the 2 TB HDD as an external drive without losing any data? Or should I format it? Yes windows HDD Fat 32 and NTFS file system can be read by Linux, so you can use it.  
My Inspiron 5570 has a 2 TB HDD powered by 16 GB Intel Optane. Now, I want to replace that Optane with a 256 GB SSD and use the 2 TB HDD as an external drive, Following are my questions Prior thanks for any help. I am trying to work this out from many days and couldn't. So, tried it here as a last hope. Please help me.
Storage configuration for Inspiron 5570