Firstly, you must identify the installer by using the command
wmic product
Look for Veeam Backup Transport
To uninstall, go to the particular folder which installer is located
C:\Windows\installer
msiexec.exec /x [installer]
msiexec.exe /x bc37a.msi [Do take note that the file may be different, that why you should use wmic to find the correct file]