Accessing Backup

I have backup of old MacBook Pro (2013 vintage) on a Seagate portable drive. When I got my current MacBook Pro I did not transfer all my programs and data over from old machine as wanted fresh start with new ID, email account etc. I now have a need to access a few documents and some emails that are on the backup drive. Do not want to a permanent transfer of all the data on the backup as the majority of it is now out of date and no longer required. I was thinking of transferring the backup to a special separate location on my current MacBook, where I can keep it all separate until I have accessed and copied the required files etc and then remove the old data. However, I am not sure how to go about it - if it is possible/feasible - and cannot see any instructions on how to do it. Would it require creating a partition on the HD? If so, how do you do this, are there any problems with such a partition, and how do you remove it afterwards?

Assistance, comments and guidance would be appreciated.

I am using macOS Sonoma 14.5.