How can I tell the wattage of my microwave?

I bought a heating pad for Cindy that you warm in the microwave, but you have to do it by wattage of the microwave.  I've looked in the manual and on the microwave itself, and I don't see any indication of what that might be.  It is a GE and very old (like 20 years - it came with the house).  I'd really like to try it for Cindy, but they're very cautionary about making sure you only heat it the exact time on the list by wattage.  I tried to search on the GE site, but it doesn't come up with this model number.  Any ideas?

Have a look on the back of the microwave, it should have a data plate (a small label about 2" big). this should have all the info about the model on it but this might have worn off if it's very old. hope this helps some.

Yeah, can't, it's built in above the stove.  I did get smart though finally, It does have a KW number, so I found a conversion tool on line to convert it to watts.  Hopefully that's accurate

I have a Sharp Carousel and the wattage--1200 watts--is listed right on the front of the microwave, right above the electronic read-out dial. I just checked.

I think one major reason they want you to be so careful is some maybe using this for newborn kittens.  I would just go with the lowest possible time and even then stop and check it a time or two and add time slowly as needed till you figure out what works.  I have heated pads like that and the rice bags all the time and sometimes the directions are off for it to be anywhere near warm enough.

I have been heating it at the lowest setting.  It gets warm.  They say don't over heat it because if the stuff inside gets too hot it could leak.  It's moot anyway, she is totally avoiding it.