Translate: Abydeni (citizens of Abydos) legatos ad regem de condicionibus tradendae urbis miserunt.

We are given that 'Abydeni' means 'citizens of Abydos'. This is the subject of the sentence; we now move to the verb, 'miserunt'. This is from the past tense of 'mittere', meaning 'to send'. So we know the citizens of Abydos sent something. 'legatos', 'envoys', is the object of the verb, which we know from the ending -os. Where did they send envoys? 'ad' implies the direction, 'towards', and 'regem' the destination, the king. So far, we have 'The citizens of Abydos sent envoys to the king.' The phrase 'de condicionibus tradendae urbis' is difficult: to start with, 'de', 'about', takes the ablative case, and 'condicionibus', meaning 'conditions', is the ablative here attached to it. 'tradendae urbis' is in the genitive case, so we can translate 'about the conditions of the tradendae urbis'. 'tradendae' comes from 'tradere', to hand over or surrender; the gerundive here gives the meaning 'to be surrendered'. 'urbis' means city. So we have 'about the conditions of the city to be surrendered.' A better translation might be 'regarding the terms of the city's surrender.'The whole translation would be 'The citizens of Abydos sent envoys to the king regarding the terms of the city's surrender.'