Try using
Everest Home Edition Computer Diagnostic Program which will tell you all about your computer. It is a freeware program.
Then if you look at
RAM Knowledge Base and use their search engine you'll find out what sort of RAM you need, if your computer is listed.
RAM is Random Access Memory and is measured in Mb (Megabytes) or Gb (Gigabytes)
Drive space is measured in Gigabytes but can also be measured in Megabytes, Kilobytes and Bytes.
A 10 Gb drive has 10,000,000,000 Bytes and that is the Decimal sizing.
The Binary sizing is obtained by dividing the number of Bytes (above) by 1024 three times.
Or you can simply divide the 10 Gb by the constant 1.073741824 to obtain the Binary size of 9.313 Gb.