Yes, it's the trade fair (actually that's the exact translation of "Messe"). The name of the quarter is "Deutz", seen from the city center (main station, cathedral,... ) it's on the opposite side of the river Rhine. You can go there easily by train, one possible station to look for would be "Bf Deutz", but since the fair area is huge, there are several options depending on where you have to go. The commuting time between the city center and Deutz is just a few minutes.

Regards,
Stefan