The installer for Mavericks is no longer available. It is the only one that Apple does not make available.
Is there a reason you want Mavericks, a 2010 Mac Pro can run Yosemite, El Capitan, Sierra or High Sierra
which are still available.
How to get old versions of macOS - Apple Support
If your mac is running a 'Metal' graphics card then it can also run macOS Mojave.
I think the only way to retain Mavericks would be to make a clone of your Mavericks drive
and use that to clone to the new SSD, this should retain the bootable properties of the original drive.
Whatever you decide to do you must make either a full backup or clone of that drive now.