In a parish record for deaths it has 3 3/4 years. I thought I read somewhere where we do not round off or put partial years so this would be recorded as 3 years. Is this correct? The form has a place for minutes, hours, days, months, years old.
Yes, you round down to the nearest full year - or 3 in this case. (It usually has the instruction in the field helps for age).
Along with the Field Helps that Melissa suggested, there is also an article in the Help Center titled "How should I index separate age fields." The link follows. To get to the Help Center, click on the question mark in the upper right corner of any FamilySearch page.