Ok fist you need to unlock the place where the rigis are. one you do battle each of the
rigis

rigirock floor 15

rigiice floor 25

rigisteel floor 35 

one you battled all the rigis (rigirock, rigice, and rigistell) you will colect 3 parts
that the rigis where guarding the rock part, ice part, and the steel part one you get the
stell part the 3 parts will conbine to make a music box. one you get to floor 98 look
arowend and stand there or mew might have tranceformed to a gloem. on floor 98 there are
only the pokemon gloem. once again mew have may trance foremed or you can stand there till
mew comes or just play the music box. try frist all of those things and then play the
music box. mew is not easy to reduct. the place where the rigis are has 99 floors. i Hope
my walkthrogh helped!!!

Enjoy meeting mew!!!