Translation:I want to look at my pictures in order to remember my vacation.
My understanding of mirar is it's more akin to to look at, whereas ver is more like to see.
However in another thread discussing 'watching television,' a number of native speakers mentioned that ver is often used in that case, so they may be fairly interchangable at times.
Seeing all the comments about the Spanish making holiday plural reminds me of growing up in northern England. We'd always say "going on my holidays" not a holiday. I don't know why (because it's more than one day?) but it helps me remember to say mis vacaciones rather than the singular version.
This isn't Duo's doing. That's just Spanish. They use the plural of vacation for vacation. I actually found this quite instructive when I discovered this as it explained why I heard Spanish-speakers say "vacations" in English. I always wondered why they consistently made that mistake and after learning how they say vacation in their language it made sense.
A simple counter-example is English speakers always including personal pronouns when conjugating verbs. Like Yo me voy, or Tú quieres?" Because in English we always say "I'm leaving," or "You want?" we assume we need the same construction in Spanish, but generally Spanish speakers don't include the personal pronoun because most of the time the conjugation of the verb tells you what the accompanying pronoun is. So overuse of personal pronouns indicates a non-native speaker.
That may be the reason, though I also can't confirm that 'the holiday' works as a translation for las vacaciones (another user in this discussion seems to indicate that 'my holidays' wasn't accepted).
You could report it. Duo does update their database of answers from time to time based on community reporting.