Question about the 6475 letters. My wife, and myself got one. It has 2,100 on both our letters. Does that mean we add them together to get the 4,200?

Yes, that is correct. The entire payment for your stimulus was $4,200 according to IRS records, which would be the full payment if your family has three members. If you do not remember getting the payment, I would check your bank records. Most people received it between March and May of 2021. The IRS should have deposited it into the same bank account that they used for the most recent tax refund on record. 

If you still have not found the stimulus payment in your records that the IRS records show was disbursed to you, it could be because:

• You were issued an EIP Card and inadvertently discarded it not realizing it was your Economic Impact Payment. You may request a free replacement through MetaBank® Customer Service by calling 800-240-8100 and following the prompts for a lost or discarded card. Please see the Economic Impact Payment Information Center — Topic E: EIP Cards for more information.
• Your payment was made to a bank account or address you shared with a spouse.

If neither of those are the reason, you can request a payment trace from the IRS. See How do I request a Payment Trace to track my third Economic Impact Payments?

• If your payment was returned by the post office or financial institution and hasn’t been credited back to your account yet.
• If none of the scenarios above apply and you never received your payment even though your online account or letter show it was issued to you.