Generally speaking, your baby will start crawling at around the 6 month mark, after spending some time wiggling on their tummy to build up their upper body muscles. By 9 or 10 months, your baby will likely be crawling with confidence (and you'll need to babyproof your doors and windows if you haven't already!)
Don't worry though - if your baby starts crawling a little later than this, it's unlikely to be any kind of serious developmental delay. Every baby is unique, and they'll reach their milestones at their own pace, though if you're concerned you can contact your pediatrician and keep them up to date on your child's progress.