Go to some memory manufacturer websites.
E.g., Crucial, Kingston, PNY, etc.
For example:
https://www.kingston.com/us/memory
There should some online tools that will either directly check your laptop's RAM or be available as a download to run and check the installed RAM.
Try two or three of the testers to get a concensus. First on the modules that will work and in what configuration(s).
Then find the laptop's User Guide/Manual. The documentation should also provide the necessary RAM specifications.