Occasionally we run into very old versions of Sage 100. These are typically defined as any version 3.x.
Thankfully, you can upgrade all of your existing data without no re-keying. Here’s how.
First, I recommend you start off at version 3.71 or higher. If you are on an earlier version you should upgrade to 3.71. I found it was sometimes possible to install 3.71 on top of ( aka in place ) the older release. If you install over the prior Sage version be certain to take a full backup first.
Next, upgrade from 3.71 to 4.3. This is the last release of Sage which offered “Upgrade Level 3 Data”.
Next, upgrade 4.3 to either 4.5 PU 8 ( the higher version may be needed if you have third-party enhancements or payroll ) and then 2017.
I found on a system with no enhancements or payroll I was able to go MAS 90 3.6x to MAS 90 3.71 to Sage 100 4.3 to Sage 100 2017 to Sage 100 2020.
Be sure you make backups of your original MAS 90 data and program files before you begin.
Finding source files for each of these versions is a bit of a project so you may want to enlist the help of your Sage partner.