Arabic bible would be of use... I think the translation of Dodo is more eloquent... if you say الرب راعي it would be a word-for-word translation... I'm not sure if this is meant to be conveyed: whether God is an actual shepherd (the noun form راعي) or the active participle راعٍ which comes from the verb يرعى : to take care of...

الله يرعانِي فَما بي مِن حاجةٍ لِأَحَدٍ

Very simple,any one of them

Oh my God! I have two answers, and they are differents, which one of these should I choose? =º

الرب راعي فلا يعوزني شئ