How to declare mexican individual retirement accounts (AFORE)?

No, unrealized gains are not reported on your 1040 tax return thus are not taxable to you. In addressing your other questions:

1. Your pension should be reported on a 8938 if the value of the account is $50,000 on the last day of the filing year or if the balance of your pension exceeds $75,000 at any time during the year. ($!00,000 or $150,000 if married Filing jointly).
2. You would need to file a 3520 if the foreign account is placed in a trust.  If you are not sure if it is a trust or not, it's best to report it just in case. A 3520 form is not supported by Turbo Tax.  Here is a form you can download here. This form can be filled out and mailed separately to the IRS. It can't be electronically filed. Here is the address to send this to: The form should be printed, signed, and mailed to:

Internal Revenue Service

P.O. Box 409101

Odgen, UT 84409

One last thing, there may be an FBAR reporting requirement. According to the CPA Journal, A foreign retirement plan is reportable on an FBAR if it is associated with a segregated foreign retirement account, since it is the foreign account—not the plan itself—that triggers the obligation to file the FBAR. A segregated account is a type of account where a company holds its clients' money separately from its own fund. 

Neither a foreign employer-created pension (which involves only a right to receive payments on retirement) nor a foreign equivalent of Social Security would qualify for reporting on an FBAR, however, as there is no foreign account to report in those situations.

If your retirement account is not a foreign employer created plan and if the value of the fund exceeds $10,000 at any time during the year, you will need to file an FBAR.. You may file this here.