Hey @LL211 ,
I have had a look at this and you will need 4 M4 screws (26-28 mm). Find more about this on page 12 in this manual: https://downloadcenter.samsung.com/content/EM/202003/20200325140559228/BN68-10528E-00_UM_UT5300L_UT4...
I returned the TV to the retailer for a full refund and bought a new one (Sony). It was simply ridiculous!!!
(When I had the Samsung I also bought two new sets of screws that were recommended on this forum but neither of them fit properly.
Bought same. It is an M4 x 28mm. Fits perfectly, its the same thread we use in Beezer boxes. Screwfix will sell them. Suggest you use the multiple snap off length ones.