I cannot find the movie rental I just purchased…need it asap for long drive…please help.

Did you look in the videos app on the iPad?

You must sync it with itunes from the macbook to the ipad.

You have to "transfer" the rental to the iPad from the Movies Tab in iTunes and then you must sync the iPad as well. You must also be connected to the internet in order to transfer the movie.

And yes - the videos app is where you watch purchased or rented movies on the iPad. iTunes is just a store on the iPad.

Rentals can only ever exist on one device at a time. If its still on the Macbook, it will not be on the iPad.

http://support.apple.com/kb/ht1657

Apple wrote:

Can I play my rental on more than one device?

• If you download a rented movie on your computer: You can transfer it to a device such as your Apple TV (1st generation), iPhone, iPad, or iPod if it’s a standard-definition film (movies in HD can only be watched on your computer, iPad, iPhone 4 or later, iPod touch (4th generation or later), or Apple TV). Once you move the movie from your computer to a device, the movie will disappear from your computer's iTunes library. You can move the movie between devices as many times as you wish during the rental period, but the movie can only exist on one device at a time.
• If you download a rented movie on your iPhone 4 or later, iPad, iPod touch (4th generation or later), or Apple TV: It is not transferable to any other device or computer.

You need to transfer the Rental to the iPad.

http://support.apple.com/kb/HT1390

Apple wrote:

Once the rental is downloaded, you can watch it on your computer or transfer the rental to a supported iPod, iPhone, iPad, or Apple TV (1st generation):

1. Connect the device and select it in iTunes.
2. Click the Movies button.
3. Select the movie, and then click Move.
4. After all movies have been moved, click Apply in the lower-right corner of iTunes.

You must be connected to the Internet to transfer a rented movie.

No problem.