Not sure what you mean how to find his medical fees. TurboTax cannot find that for you. Your dad's own records have to be used. Or call the doctor's office to ask for a print out if they can provide it.
Does your father have enough itemized deductions to exceed his standard deduction? If not, entering his medical expenses will not make a difference.
The medical expense deduction has to meet a rather large threshold before it can affect your return. The amount of medical (including dental, vision, etc.) expenses that will count toward itemization is the amount that is OVER 7.5% of your adjusted gross income. You should only enter the amount that you paid in 2020—do not include any amounts that were covered by insurance or that are still outstanding. Of course, your medical expenses plus your other itemized deductions still have to exceed your standard deduction before you will see a difference in your tax due or refund.
To enter your medical expenses go to Federal>Deductions and Credits>Medical>Medical Expenses
Does he make a copayment, or are his expenses covered by Medicare or other insurance in full? Also, FYI, the TT Medical expense categories are just for your use. Only the total ends up on his tax return.