Page 10 in the Dell manual lists all the screws/sizes.  Probably best to just try and get them yourself.  

https://topics-cdn.dell.com/pdf/inspiron-15-7590-laptop_service-manual_en-us.pdf

@Michael_Dell_User 

Home Depot sells M2 x 4 mm https://www.homedepot.com/p/Everbilt-M2-0-4-x-4-mm-Phillips-Flat-Head-Stainless-Steel-Machine-Screw-2-Pack-843438/204852270  which are 1 mm shorter than the 5 mm that you need but should work.

Otherwise, you can buy the screws from Amazon or on eBay ( https://www.ebay.com/itm/M2-Phillips-Flat-Head-Countersunk-Machine-Screw-Steel-w-Black-Oxide-DIN-965/122467347086  )

I can't tell from the manual if the three captive screws are the same as the five base screws.  They appear to be longer.