Electric Thermal Relay

Check the nameplate and applied voltage and current tag on the motor.

That depends on a lot of things. From the sparse amount of information you give us, I doubt you'd understand what needs to be known.

The rating or ampere of thermal overload relay should be low enough to protect the wiring, but not so low as to hinder operation of the motor, if properly sized and installed.

As already mentioned, you will need to find a competent local electrician to enlighten you.

The OCPD protects the cable and starter, the thermal relay the motor.

You can get combined units from some manufacturers.

Set the relay to the value on the motor rating plate, better still get a qualified electrician to do it for you.

Use proper formulas and/or manufacturers recommendations...

https://electricalnotes.wordpress.com/2013/06/02/calculate-size-of-contactor-fuse-c-b-over-load-relay-of-dol-starter/

P=I*E

You gave us the P, want to know the I and didn't think or know that we need the E.

I say your over your head so call an electrician.

There is only one answer, already given. You MUST read the motor nameplate full load amps, then select or adjust the OL heater element or dial adjustment as per the instructions provided by the manufacturer. There is no other accurate method of accomplishing proper motor protection, everything else is just a guess, and guessing is for gamblers, not engineers.

The protocol is in British Standard 7671.

Try

BS 4941
BS-EN 60947
IEC 292
IEC 947.

1) Is it a European (IEC) or North American (NEMA) motor? NEMA motors have a service factor, already comprehensively covered.

2) Is it a DOL starter? Or is it a star-delta starter with the relay within the delta? The setting in this case will be 1/√3 of the rated current.

Easier to look at the manufacturer's recommendation from the catalogue - here is one example from Schneider Electric :

My guess based on the 35kW description would be an IEC motor. So no Service Factor involved. We don't use kW for mechanical power here, we use Horsepower, because horses were here first (James Watt rode one!) and are cuter than James Watt was (or so I'm told).

Giving a simple question as "What is the rating or ampere of thermal overload relay to protect 35kw of electric motor(3phase)?" is a job of non electrical personal. As an electrician personal they will also include other data's like the "rated voltage" and "rated frequency" so that calculation can be done with all these data's.

The setting within 125 percent of rated current and time dial could set to min sellection