I have a 2005 Trek 1000c:
archive.trekbikes.com/au/en/2005/trek/1000c#/au/en/2005/trek/1000c/details

I am interested in buying this power meter:
store.stagescycling.com/Stages-Power-meter-Dura-Ace-7900

The description says "This Shimano Dura-Ace 7900 based Stages Power meter is compatible with all Shimano Hollowtech II road drivetrains."

I am assuming they are talking about the bottom bracket? Correct me if I am wrong.

I am new to bike mechanics. How do I know whether my bike's drivetrain is Shimano Hollowtech II or not? And if it is not, can I replace it with a Hollowtech II?

The other question is regarding crank length. Mine is 170. But the Dura Ace above is only available in 167.5. Would that be a problem?

If all else fails, is there any power meter either from Stages Cycling or some other company that is compatible with my bike?

If this is not the right forum for this, kindly move it to the right one. Thanks for being patient with a newbie.

I'm assuming you know that you'd have to change out the crankset to make a power meter like this work with your bike. You have the original crankset like the one listed in the specs (triple)? But basically you'd need to change the bottom bracket to a hollowtech ii (yours is probably just a regular square taper), get the compatible crankset, and upgrade shifters too. You'd probably be better served going with a pedal based solution or a powertap wheel.