It is not possible to delete the Safari app, so it's somewhere. There are a couple of possibilities.
I'm going to start by assuming you are on iOS 7 or 8. If you are on an earlier version of iOS the details will be different.
1) It has moved to another Home Screen or is in a folder. You can confirm that Safari is on your iPad by using Search. While on any Home Screen, swipe down in the middle of the screen. You should get a search bar at the top. Type in Safari. Look closely to see if it says it is in a folder, and the folder's name. it will be to the far right of the app's name.
Now, go find the folder.
If the app does not show up in the search results, go to Settings > General > Spotlight Search and make sure Applications is checked.
You can launch apps directly from the search results, which can be handy if you have a lot of apps and get tired of searching for them.
2) You've disabled Safari in Settings > General > Restrictions. Restrictions are protected by a passcode. You do not want to forget this passcode. It's very difficult to get around lost passcodes in iOS; as it should be.