Hopefully, you still have the .exe installation files from when you first bought MSP13. If you have, simply copy/paste those installation files to your new computer and then run them. You'll also need your MSP13's serial number in order to activate that program. This can be easily found on your old computer by going to Help/About in MSP13.
If you haven't got the installation files, go to the My Products listing in your MAGIX My Account where you should find the installer for MSP13 - assuming that the data transferred from Sony to MAGIX aafter MAGIX acquired the Vegas product line in 2016.
VMSP13 was also released as a Magix rebranded version which is what I have. Unfortunately my download link doesn't indicate the build number and I no longer have it installed to check.
EDIT: I've found my archived VMSP13 file and it's Build 987 for my Magix rebranded build.