You already have 2 M.2 slots on your motherboard that appear to be unused.My good God, a lot of this has gone over my head...but thank you so much!!
I contacted PC specialists and they suggested for me to buy this expansion for M2 cards:
Hyper M.2 x16 Card V2|Motherboards|ASUS Global
ASUS offers different kinds of motherboard accessories including Thunderbolt™ expansion cards, M.2 add-on cards, and fan extension cards give DIY PC users better choices when it comes to building their perfect workstation or gaming rig.www.asus.com
They told me that this will allow me you to mount 4 more m.2 drives (my motherboard can accommodate 2), but only in PCIe 3.0 speeds.
I was going to use the maximum RAM in my PC in the future.
I think I will also invest on the above.
Thanks so much to all here, you have been extremely helpful!!