They utilize 240-pin PC3-10600 DDR3 DIMM sockets. You can often max them out at 4GB.
Because the specs are modest, they perform significantly better with lightweight operating systems like Lubuntu or Puppy Linux . Are they Epson Printers? ET1850_ET1851
Replacing the aging 500GB HDD with a cheap SATA SSD is the single best way to make these machines usable for basic office tasks today. They utilize 240-pin PC3-10600 DDR3 DIMM sockets