Um... I don't think the planner actually edit your save file.
Just to make sure I understand what you're saying, though... you've already copied your Android save to PC, and now you want to edit the save file to change it from the current farm map to the beach farm map. Have I got that right?
If so, I'll caution you... the path you wish to take is fraught with pitfalls galore. Some objects are populated by the farm map and then there's other things you've placed... and then when you edit the save file, suddenly things are where they shouldn't be because of obstructions on the new map. I really,
really recommend that you just start up a new save file on your PC on the beach farm map and have fun.
However, if you're dead set on editing your save file to change the farm type, first thing you need to do is make sure you have a backup. Double check and make sure you have a backup because you don't want to screw this up so bad you need an "undo" but don't have any. Next, go to this recent post on a recent thread that explains the process in detail:
Can I change farm type mid game? Just note that I do not know for certain, but assume the 4-Corners farm is
5 and Beach farm is
6 when following those instructions. Also, pay special attention to the caution given about using the planner to better rearrange what you have on your farm in preparation for what happens after you edit the save file for the map change.