You can copy all the files from your 4GB SD card to your 128GB SD card to keep your progress.

i formatted my sd card without realising all my data was on it including videos of my older brother wrestling from when i was like 6

that happened to me, i had so many videos of me playing with shopkins when i was like 7, lol i think i accidentally made lost media

you can transfer your data, that's what i did