where is the adverb

[Unregistered]

Dad drove backward intot the garage.

[indonesia]

I would assume it's backwards, because it is tellling us how dad drove.

Dad drove backwards into the garage last night.
Dad drove carefully into the garage last night.

Both words are modifying the verb 'drive'.

[Kondorosi]

Adverbs serve two major roles: they can be integrated into an element of the clause, or they themselves can be an element of the clause. In the first case, the adverb serves as a modifier; in the second case, the adverb is an adverbial.

When adverbs are modifiers, they usually modify an adjective or another adverb.
There are no (adverb) modifiers in your sentences.
The adverbs serve typically adverbial functions.

1. Dad drove backwards into the garage last night.
2. Dad drove carefully into the garage last night.

In #1, there are two circumstance adverbials:

• backwards (manner) (both backward (AmE) and backwards (BrE) work)
• into the garage (direction)

In #2:

• carefully (manner)
• into the garage (direction)
• last night (point in time)

[bhaisahab]

Of course, no native speaker would ever say "Dad drove backwards into the garage", except possibly a small child. We would say "Dad reversed into the garage".

[Kondorosi]

Drove his car against the garage door?

[bhaisahab]

Drove his car against the garage door?

Do you mean "drove into the garage door"?

[Kondorosi]

drove into the garage (door) = collided with the garage (door)

[bhaisahab]

drove into the garage (door) = collided with the garage (door)

Yes, that's what it means. Is that what you wanted to say with "drove against the garage door"?

[Kondorosi]

Yes.