What temperature should chicken breasts cook in the oven at and for how long?

Buy some parchement paper and wrap them inside packets, you can even make on big packet if you want. Check after 25 minutes. This is more steaming than anything so it comes out really juice, but you need to let them rest. Or take them out and if they're around 160, you can try putting them back in uncovered to brown some. This is how I usually make mine for freezing or quick chicken salads, etc. Really good if you put some pesto in there with them, or S&P and some olive oil.

Cook until internal temp hits 160. 350 for 25 to 35 minutes should do it.

350 degrees for about 45-55 min. depending on the oven and check them after 30 min.