how do i pronouce the french word modèle and a larrèt?

You got the spelling wrong:

a larrèt should be written à l'arrêt

musèe d'art should be written musée d'art

Modèle -> mo - deh - le

à l'arrêt -> ah lah - reh

musée d'art -> mu - say d'ar (mu as in amuse, but make the u flat, d'ar as in dart, but no t at the end)

None of the h above is pronounced.

-mo-dèle --the first "e" is kind of like "eh (an abrupt upside down e in English, if you will)" sound and yes, you do pronounce the "le" in the end. Unlike, the second word, larrèt, which would be pronounce --la-reh and you don't pronounce the "t" in the end, unless you misspelled the word.

Oops...I forgot about your second question. It would be musèe d'ar (don't pronounce the "t" in the end and it won't da-ar, it will just be d'ar).