Install older version

Hi,

I'm running High Sierra and my iMac started to give up yesterday.  I unistalled AE, and because I don't have a version installed anymore, it won't give me the options to install pervious version.  The OS prevents me from installing any newer version that CC19.

Any ideas how to get around this? I basically just need to collect and reduce a few projects onto drives to move onto a new machine.

Thank you