lost my bookmarks in safari

Mac Pros are desktops. MacBook Pros are "laptops", or really technically "notebooks" since no notebook since 1994 was cool enough to maintain on one's lap indefinitely without burning your skin.

As for your problem, did you backup your data somehow before upgrading? If not, you may be able to recover them using tips here:

https://discussions.apple.com/docs/DOC-1689

Note, bookmarks are user specific, so if you imported data into a new user, it may have lost track of the location of the file. Users -> yourname -> Library -> Preferences -> or Users -> yourname -> Library -> Application support are where Apple stores most user specific documents.

I'm about to upgrade my MacBook Air from OS X 10.7.5 to the latest version of El Capitan and want to ensure that I don't lose my bookmarks in Safari. I've done a backup. Do you have any tips on how they can be transferred smoothly with the upgrade?
Thanks!