Intel ARK lists the S3500 SSD as being compatible with the R1304RPSSFBN but the drive bays in this server only fit 3.5" drives.
For the entry level fixed pedestal servers, the hotswap pedestals servers and the hotswap rackmount servers there is no problem as the drive trays support both 2.5" and 3.5" drives.
How do Intel suggest the S3500 series can be fitted to the R1304RPSSFBN is there a 3.5" drive sled that is approved?
Check page 4 (14 of 82) of the R1000RP TPS at Server Products — Technical product specification
The 3.5" HDD systems can only support 3.5" HDDs or SSD. It cannot support 2.5" HDDs.
So, as long as you are using SSDs, you are okay. There are mounting screw holes for them.