L0velyAmethyst

Go to your local discount hardware store and buy a tap and die kit. You can then re-thread the screw holes properly and get some slightly wider screws (from the same hardware store) and it's job done. 

It's going to be more difficult given the screws are so small, however some things that I've used in the past will get the job done:

Take a Dremel to them and cut a slot for a standard screwdriver (delicate, being sure not to split the head in half)
Stripped screw extraction kits
Some strong form of epoxy (something that solidifies as a solid), patience (or something to securely hold your sacrificial screwdriver in place, properly), and an understanding that you're likely to make the screw, and the screwdriver itself useless as a result.

Then there's always the more barbaric, but again difficult given the size of the screw, plier method, it's going to booger the screw and your IO shield up.

Bear in mind that the 660p supports 3.0, but doesn't requrie it - it will work in 2.0
Also, the theoretical bandwidth of Pcie 2.0 x4 (2 GB/s) is slightly higher than the theoretical speeds of the 660p reported by Intel.

2x M.2 ports (Key M)
*M2_1 slot (from AMD® processor) supports PCIe 3.0 x4 (1st, 2nd and 3rd Gen AMD Ryzen™/ Ryzen™ with Radeon™ Vega Graphics and 2nd Gen AMD Ryzen™ with Radeon™ Graphics) or PCIe 3.0 x2 (Athlon™ with Radeon™ Vega Graphics) 2242/ 2260 /2280/ 22110 storage devices
 
M2_2 slot (from AMD® X470 Chipset) supports PCIe 2.0 x4 and SATA 6Gb/s 2242/ 2260 /2280 storage devices
 
*SATA1 port will be unavailable when installing SATA M.2 SSD in M2_2 slot.
*PCI_E6 slot will be unavailable when installing PCIe M.2 SSD in M2_2 slot.

That works out perfectly. Thanks