You can find the infinitive phrase by placing 'to' in font of each of the words. My teacher taught me this. Whichever statements make sense are the infinitive phrases.
So lets begin:
To before
To the
To show (show the noun; like event, so 'to event')
To they
To went
To to
To find
To the
To water (again the noun; like liquid)
To fountain
Of course the only phrase that makes sense is 'to find', so I believe the statement beginning with 'to find' is the correct answer.
'to find the water show'
Sorry this was long, but hope it helps anyways :)