If you've never read Plato before, I'd suggest not to start with the Republic — it is diving into the deep end of Plato. I'm saying this as someone who has recently completed Republic[1], and thoroughly enjoyed it (and fumed at it in some places).
Instead, get familiar with some of the earlier, and famous, Socratic dialogues: Euthyphro, Apology (this is referring to a "formal defense", i.e. apologia; not regret), Crito, et al — they're shorter, give you a great flavour of Socrates, and will prepare you for the Republic. An excellent English translation here is the Five Dialogues[2], a fine selection by Hackett Publishing. I'm happy that I started with this.
[1] There are many English translations; I'll strongly recommend the "Reeve Edition". This translation recasts the entire dialogue as direct speech, this makes it easy to keep track of the speakers. Ensure it is this Reeve-only edition (because Reeve also revised an earlier translation by Grube): https://www.hackettpublishing.com/republic