You need new bars, flat bar brakes/shifters. It can be expensive.

I would say its more cost-effective to sell your road bike and buy the hybrid bike you want.

You should consider a drop bar bike geometry may not work well with a flat bar setup.

The cheapest way to convert your road bike, is to install a stem riser and moustache bars. That would give you an upright riding position for not very much outlay and you can keep your road bike drop bar brifters.