Hello I Stopped Smoking In December When I Found Out

Hello
I stopped smoking in December when I found out I was pregnant - I used an e cig for two weeks then stopped. Sadly I had a missed miscarriage which was discovered at ten weeks. I started the e cig again but am planning on trying to conceive through Iui in September. I want to stop the e cig and wondered what recommended time is to stop by before the Iui treatment please. I want to stop so I'm as healthy as possible
I just turned 35
Thank you