Can I use Driver Booster 6 to add all the drivers when I install a new Win7 operating system?
For now, I would assume yes. As long as the database that Driver Booster uses has valid links to the drivers you need for Windows 7.
However, don't expect that situation to last long anymore.Windows 7 is very near to "being put out to pasture" by Microsoft and driver support will become sketchy after that happens. You can get all the drivers you'll need for your Windows 7 computer yourself and either store them in a safe location or create a new installer DVD or pendrive with all these drivers already included.
That will have your driver needs covered, but you Windows 7 system won't be getting any security updates anymore and that is of much greater concern than not having the latest drivers. Don't use that system anymore for doing anything online that requires your credit card for example. From that moment on, it is wise to not connect that Windows 7 system to the internet at all anymore, if safety is of any concern to you. And if that Windows 7 system is part of a home network with several (Windows) computers, then the Windows 7 pc can be used to enter your network and attack your other computers too.
Security wise, it is better to migrate that Windows 7 system to Windows 10 (to have Microsoft support again) or find an alternative (supported) operating system for that system. Linux Mint or Ubuntu are decent Linux distributions for which you can expect support now and in the future. Or live a little and use a lesser known distribution to increase up your computer skills.