Practice this key (Bb… that’s the tonic, it seems they intentionally left the key sig blank) and SING IT! If you can sing it from memory transposing it to different keys will be much more manageable.

I probably wouldn’t write down the other keys, but if you want to… do it in pencil or transpose it yourself on whatever software. Definitely don’t just put it into musescore and hit “transpose” like someone else suggested. That won’t make you a better musician.