lost programs when changed the windows on my computer

I posted this earlier today but can’t find it, have no idea where it went off to…

I purchased Avast primer and Easy Pass in March of this year. Then we took windows 8 off of my computer and put windows 7 on here so I lost them both when we did that.

How can I get them back on my computer? I am using the free Avast but it runs out in about a week.

https://forum.avast.com/index.php?topic=174430.0