I want to offer free shipping with print on demand

[Webmania30]

I hope this is the right board for this type of question. I just started an e-commerce store to fundraise for my nonprofit and after trying it out for a few months, I've decided that I want to offer free shipping but the problem is that I've already set the prices and I have 179 products. I use both Printify and Printful. I either want to offer free shipping for over a certain amount, like $25 or I want to offer free shipping period. Obviously, I can't afford to pay the costs for this out of my pocket so how do I raise the prices on all of my products AND offer the free shipping short of shutting down my site to get this done. I'm really new to this and I'm assuming this is the way I'll need to do this. Will I need to find out what each item's cost to ship is and then add that on to the price for each collection. I see there's bulk edit apps, but I am a very small nonprofit and I'm already paying out more than I'm taking in, lol, although I hope to change that soon. Thanks for your help in advance. If this is the wrong board, please point me in the right direction