Trying to Locate old Bitcoin — where should I start

Hi everyone, I’m looking for some guidance on how to begin a search to locate old Bitcoin that my dad purchased. We know he bought Bitcoin, but unfortunately don’t remember where it was stored or what wallet/service he used. Here are the few facts we do know:

• The Bitcoin would have been purchased/accessed from one of his old Windows laptops (primarily Dell computers), and we still have backups of his old devices/files.
• He still has access to both email addresses that could potentially have been associated with it.

I realize this is basically searching for a needle in a haystack, and I’m not expecting this post to give me an easy answer, Im more so just looking for direction on how to search because I don’t know enough about older Bitcoin to know where to begin.

Any advice would be appreciated even something as simple as any search terms, old wallet names, files to look for, or helpful resources on YouTube or Reddit would be appreciated.

P.S., any scammers reading this, save yourself the time. My messages are turned off, I will not provide any private info, and to stress one more time I’m only looking for advice that can be shared publicly in the comments. Thanks in advance for any direction!