How much to change manual car to an automatic?

This can be a fairly easy operation IF the car has rear wheel drive: simply described, one needs a transmission that is compatible and can bolt up to the engine. You'll need to change the gear selector inside the car, too.

If the car is front wheel drive, you may need to replace the entire engine since the transmission is in integral part of the engine. That could be quite costly.

Go to some transmission shops and get an estimate. The costs will vary greatly based upon the car manufacturer, region of the country, and the individual shops themselves. There is no "standard fee chart" for determining the final cost.