@Odin1970
If you have used turbotax in the past and still have your files or access to your account, it would be easiest to do it in order.
To amend your MFS returns from 2023 to joint, you pick one of the MFS returns, change the status to joint, and add all the other's spouse's income and deductions. When that return is submitted, it will automatically cancel the other MFS return. You have to be careful about how you report tax payments and refunds, so the adjustments come out correctly. See this FAQ.
https://ttlc.intuit.com/turbotax-support/en-us/help-article/amend-tax-return/amend-married-filing-se...
For 2024, you will not use the amended 2023 joint return as a base, you will again pick one of the MFS returns and amend it to joint. It would be best to use the same spouse as the #1 spouse on the amended return.
Then for 2025, you can start by using the amended 2024 joint return as the base.
