Sheep are defenseless animals that wolves often attack. Jesus is stating that people may harm the disciples. AT: "as sheep among people who are like dangerous wolves" or "as sheep among people who act the way dangerous animals act" (See: [[rc://en/ta/man/translate/figs-simile]])
Jesus is telling the disciples they must be cautious and harmless among the people. If comparing the disciples to serpents or doves is confusing, it might be better not to state the similes. AT: "act with understanding and caution, as well as with innocence and virtue" (See: [[rc://en/ta/man/translate/figs-simile]])