So sorry for your loss. Did he use the Desktop software program installed on the computer or the Online browser version? If he used the Desktop program then the tax return is only on that computer. Maybe he made backups, like on a flash drive or something? You need the file ending in .tax2024 to transfer into 2025.
If he used the Online version you would need to know his account username and password to get it.
Do you have a pdf or copy of the return? You can get it from the IRS. But that won't transfer into 2025 Turbo Tax.
Request a transcript from the IRS
https://www.irs.gov/individuals/get-transcript