You will need to update your IOS versions to support VTPv3. The first step is to determine which IOS version is suitable for these devices and which one supports VTPv3.
First go to the software download site of Cisco at the following link:
Choose your exact model for the 3750 and 3550, select IOS software if you are given the choice, and then look at the column on the left to see the latest IOS that is suggested for use with your device. (the one with a star beside it).
Make a note of that release (you may have several versions in the file list, the ipbase is sufficient for what you need, but you can jot down any of them.)
Now according to the Cisco feature navigator found at the following link:
these are the IOS versions that support VTPv3 at the bottom left of this image:
Go back and see if your switch supports any of these. If it doesn’t, there is unfortunately no way to get VTPv3 to run on your devices. If it does, then the next step is to obtain that particular IOS file.
How do you obtain such files? Do a bit of research on the web, and at the GNS3 web site and forum as well and you may be able to find out how.
I hope this has been helpful!