Advice on Tank Change?

Hey all! Our Axie, Jellybean, is currently 10m old, and 8 inches long. We got her in a 20gal for her baby months, but now that she's bigger, we are moving her to a 40gal. We bought the tank, but I'm unsure how to best move her and the water. The filter will be the same because when we put her in the 20gal, I bought a 40gal canister filter (we always knew we'd be moving her to her bigger home). We also have a water cooler, 2 hides, and plants (currently in her 20gal). What is the best way to transition her? Do we move the filter first and let it run in the new tank for a while? Do we put her current water into the bigger tank and add more (obviously treated)? Or do we do all new water?