Drop bar to flat bar conversion
It's almost certainly going to be more cost effective to replace the whole bike, and selling the current one.

There are potential problems with both brake caliper and derailleur compatibility going to flat bar shifters.

Aside from replacing shifters, drivetrain and bar, drop bar road bikes have shorter frames than flat bar bikes, because the rider's hands are placed forward of the stem head on the drops or hoods, but a flat bar places them approximately level with stem head. You may find the seat to bar distance is too short with flat bar installed.