I am submitting my review for a journal but they ask for a letter with peer review suggestions (3), but it is not templete, and i am not sure if I can suggest any peer for the review or they have a specific list. Thanks.
If I'm interpreting your question correctly, you're asking about how to respond to a request for potential reviewers by the editor.
It is what it looks like on face value - you suggest potential reviewers, which the editors may or may not use. There is no "list" to choose from. You can suggest anyone as long as they have the technical know-how to review your paper. You should avoid suggesting people who might have a conflict of interest with you (so e.g. other members of your department are excluded).