Sloghtly OT-memory for laptop? memory selecter, bu

Hi all-
I have a slightly older generic (sager) laptop.
Intel P4 2.0, but only has 256 of memory.

How can i tell whet kind of memory to use?
I used the website selector, but it didn’t help at all!

is there something in divice manager etc… that I can check for what kind of memory to buy?