Currently, there is no direct way to change the class tracking to location in QuickBooks, Bob.
As a workaround, you can manually recreate your Classes as Locations. Here's how:
Go to the Gear icon, then select All lists.
Click Location, then New.
Enter the name of the Location based on your Class list.
Hit Save.
Once done, you'll have to update each transaction manually to replace the Class field with the corresponding Location. If you're using QuickBooks Online Plus, you can use the Batch Transactions feature to simplify this process.