I am going to assume here,
1. the traditional IRA contributions for 2024 were not deductible (because you were over the income limit for a deduction),
2. your 2024 return documents those non-deductible contributions on form 8606,
3. you plan your 2025 contributions to also be non-deductible,
4. you have no other traditional pre-tax IRA funds anywhere (all IRA funds are combined for tax purposes even if they are at different brokers).
In that case, you convert the entire IRA account and only the gain (earnings more than the contributions) are taxable.
If any of those assumptions are not true, we need more information.
