Currently, Adobe Firefly Image 2 and Image 3 generate at a 2K resolution. At 300 DPI, that would mean:
Widescreen (16:9) -> 8.96 in x 5.12 in @ 300 ppi
Square (1:1) -> 6.82 in x 6.82 in @ 300 ppi
Portrait (3:4) -> 5.97 in x 7.8 in @ 300 ppi
If you are needing a higher resolution than that, then I would recommend trying to use Super Zoom as part of Neural Filters in Photoshop. That can easily double or even triple your resolution, which is fine for many print sizes.
Depending on the type of image you are also generating, if it is a more illustrative generation, you can also taking the image into Illustrator and using Image Trace to turn it into a vector image, which would give you infinite scaling.