Yes it is! You are the new owner of a 12V motor.
You will need a white gear to power a knex rod. I hope (assume) it was included in the bunch you got.

Also I hope the original K'NEX mains adapter is present.
 

here you can find more information about this and how to install it:

www.knexusergroup.org.uk/en/knex-hint-M3.html

I could try to explain it, but a picture will tell you more!

 

If the adapter is not present, you can use any other adapter which is 12V and 500mA or more and has the same output connector. The polarity is not so important, as it is an DC motor, only the turning direction will be changed.

Yes it is! You are the new owner of a 12V motor.
You will need a white gear to power a knex rod. I hope (assume) it was included in the bunch you got.

Also I hope the original K'NEX mains adapter is present.
 

here you can find more information about this and how to install it:

www.knexusergroup.org.uk/en/knex-hint-M3.html

I could try to explain it, but a picture will tell you more!

 

If the adapter is not present, you can use any other adapter which is 12V and 500mA or more and has the same output connector. The polarity is not so important, as it is an DC motor, only the turning direction will be changed.

 

The bunch didn't come with the worm gear sadly, so I'll just have to order one from the knex website.

 

I don't exactly have a 12V and 500mA adapter, the closest one I have to that is a 15V 3A adapter.

 

Is the higher amperage and voltage going to be a problem?

I find this quite humerous, as I got an almost complete HTT set about a year ago. I had the white micro teeth gear and the 12V adapter, but the motor itself is missing. It seems I have the exact motor components that you don’t.