It depends. One variable is whether you used the standard Windows 7 Backup and Restore or a 3rd party backup application or another version of Windows. The following applies only to Windows 7 Backup and Restore.
Windows 7 Backup and Restore has the ability to create both a system image backup and a data backup. The system image includes everything on the Windows machine and the data backup includes just user libraries and data files. It has the ability to make both backups as part of a single backup procedure. I know of no way to access the system image backup from a Mac.
You can access the data backup however. If you connect the external drive to your Mac and open Finder and click on the external drive in the left side panel under devices, you should see 2 folders related to the Windows backup. One will be named WindowsImageBackup and I know of no way to access that. The other will named after your old laptop. You can open that folder and inside there will be one or more folders named Backup Set plus a date. You can open those folders and inside will be a folder named Backup Files plus a date which you can also open and that will have a number of .zip files which you can open by double-clicking. Doing this you can drill down to actual data files. You can copy the data files to your Mac; one way is to open a second Finder window (File menu command New Finder Window) and navigate to the location you want to place the files and then drag the files from the external drive Finder window to the Finder window open to your Mac drive.
The above will not be fun and could be very time consuming but if the only copy of the files is located in the Windows Backup on the external drive, it would be a way to get them. The "Manually Migrating" section of Switch Basics: Migrate your Windows files to your Mac has some information on the folder locations where you may want to move the files to. (Note -- as far as I am aware, the Migration Assistant mentioned in the above link will not access the backup.