Which episodes show nude women in Family Guy?

None of them really. If a character is naked it's either partial, strategically covered or outright censored.

Meg was naked when she showered with Peter in Dial Meg for Murder, although not nude, she takes off her shirt in Fish Out of Water.

Lois is naked when she's high in Deep Throats, she's also nude when they invited Jeff Campbell over in From Method to Madness.

Brian & Stewie have a (censored) topless woman on their radio show in Mother Tucker.

Jillian drops her towel in front of Brian in Whistle While Your Wife Works.