"I need to delete some but it won't let me because it says the item was used. If I could find where it is used I can delete the Estimate it was used on but I don't know how to find the Estimate"

Yes, I described it: Reports menu > Jobs, Time and Mileage reports. There is "Item Estimates Vs Actuals" right there; filter it for the items you want, which cannot be Left Inactive to Filter on them. They will show, if there were used, even if left inactive. Set your date range at the top to ALL.