How could I measure RF transmission power from SMA connector without having a RF wattmeter equipment?
Short answer: you can't.

If you want to measure power at radio frequency, you'll need a device designed to do so. Your multimeter is specifically designed to suppress RF, as it's pure noise to the things it's designed to measure.

What you'd need to do is build a converter from the RF signal to some slow signal that your multimeter could measure. But building (and calibrating) that is actually the hard part of building an RF wattmeter.

So, no, you can't.