In order to migrate a question to MathOverflow one should flag it for moderator attention and request that the question will be migrated. Either the moderator who handled the flag is sufficiently knowledgeable in the field and can do it themselves; or they consult a MathOverflow moderator/user for the suitability of the question to that website. Then they migrate the question, or decline the flag.
HOWEVER your question is over 60 days old. Therefore it cannot be migrated.
You can use this dedicated thread on meta.MO to try and attract some attention to your question from MathOverflow users. The catch is that if the people who can give you an answer don't follow meta.MO, or didn't check this thread specifically, the question will go unnoticed.
But as an initial first step, I'd say that's a good thing to write in this thread and try to get some attention.
You can cross-post. This means that you just re-post your question on MathOverflow, with perhaps some minor changes. There are some basic guidelines for doing so, such as giving the link to the Math.SE question and writing explicitly that the question was posted on Math.SE before; there's also the timing factor (i.e., never cross-post within the first 48 hours and preferably not in the first week or two), but in this case the question is already too old for migration so there's no problem with that.
So my suggestion would be to post on the meta.MO thread, and if after a few days there is still nothing new, cross-post it to MO and add a comment under your meta.MO post (and the question here) that the question has been cross-posted, with a link of course.