I'm not sure what you mean by "convert" points. I can only assume you want to take X number of AP points and change them into X number of MP miles. This cannot be done directly (only through a transfer through a third party like points.com (which UA doesn't participate in) or through something like AMEX membership rewards, others can probably comment on the ways to best do this, though, you likely won't get 1 to 1 conversion).

UA also does not currently participate in *A upgrade program (they used to). Rumor over on the UA forum is that they will be involved again in the future, but I don't think anyone knows when.