How many e sim support 12 mini

You can have multiple eSIMs installed in the phone.

However, a maximum of 1 eSIM may be active at any one time.

See additional info here:

Using Dual SIM with an eSIM - Apple Support

Note that for your “12” the “Dual SIM” capability refers to 1x eSIM + 1x nanoSIM being active simultaneously.

Only one active eSIM at any given time on iPhone 12 models