How i should calibrate TCP on gripper?

Such simple grippers like this, direct entry is most easy and effective.

Two things you have to find out is:
The rotation around Z-axis.
Center (Z-value), what do you want, in the middle of the curve or end of gripper...

Looks to me like the gripper is designed to hold cylindrical parts - I would set the TCP so that it's in the center of the cylinder (right between the fingers), with Z pointing away from the flange and X pointing up when the robot is in zero position.

Wait !!!!!!!!!!!!!! Is that a cow in the background ?

Does the robot still run when the cow steps on the cables sitting on the floor?

That is a plastic cow...

Between the fingers, just a direct entry with an offset on Z. Seems like the best solution for whatever it is you're trying to do...

Just don't try to milk the cow with it. She may not like it.

If you want to milk the job you might as well setup your tcp orientation as follows for a more intuitive orientation

tool X moves the gripper forward/backward
tool Y moves the griper sideways
tool Z moves the gripper up/down

Using W,P,R angles : 90, -90, 90

If your gripper jaws are not horizontal when robot is at zero position, rotate J6 until gripper is leveled then
subtract the J6 angle value to 90, that's your W angle

The center of the TCP looks to be at the center-line of the 6 axis at some distance form the face-plate, so
TCP X,Y,Z should be 0,0,z