[NAME] - Many users around here buy RAM for Dell PCs from Crucial. Better prices and they guarantee it will work or they take it back.  You only have two RAM slots so you could add one 4 GB module or, better, install a matched 2x 8 GB pair, or even more depending on your needs and budget, keeping in mind that the i3 CPU still will be a bottleneck which you can't overcome just by adding lots of RAM. You can check Dell's specs for RAM configs supported in this model.
Hi, I just purchased an inspiron 3880 to replace my older vista machine, and it has really been a big disappointment to say the least. It is so slow at everything it does and I mean everything. Just to turn it off takes anywhere up to 30 seconds to bring the menu up. It acts to me like there is to much stuff running in the background and it cant keep up. But if anyone here can give me a clue I would appreciate it. And any command whether it is just system related or going to the web, takes way to long. I have always used firefox and thunderbird e mail with no troubles but it might take up to 3 minutes to open either one and the same with the Edge browser. I am very unhappy with this thing, its bad enough having to run Windows 10, but this thing is a real let down. Any help would be welcome. thanks. 
Inspiron 3880 Unbelievably slow