SD card issues with Nikon D40x camera?

I just bought the camera and bought a Sandisk 64gb sd card but when entering it, the camera responds with "Card is not formatted, format the card." I'm not very familiar as this is my first camera so what does this mean and will I be able to correct it?

You bought a camera that was made long before SDHX (64 gb or larger) were developed.

You need to buy SD cards that are 32 gb max.

This is all in your user manual and if you do not have one, you can down load one from NikonUSA.com

As far as formatting a card, you need to do this routinely. There's a format feature in the camera's manual.

The workflow you need to adopt the following process

* At the end of each shooting day, remove the memory card from the camera and insert it into the card reader on your computer
* Using your computer skills, copy all the image files to a new file folder you have named for the subject/location and date so you can find your photos years later
* Once all the images are safely on your computer, remove the card in insert it into the camera.
* Then use the format feature on the camera to format the card.

Usually, if you do this, you will not need a card with a capacity larger than 4 gb. Just buy a few and keep them with you. If you buy Class 10, UHS-I cards they will be viable for the next five years or so. As sensors become populated with more and more picture elements (pixels), individual RAW and JPEG image files will become larger, so faster read/write cards will be some thing you will want to have

The camera may not know how to deal with such a large capacity card. Check the manual to see what kind of card is recommended by the manufacturer. This support page implies that 4GB is the top end as of 2016, though there may be others that will work:

"Approved Memory Cards - D40X"
https://www.nikonimgsupport.com/ni/NI_article?articleNo=000002535&configured=1&lang=en_US

Get out your camera Instructions Manual; check the index for memory card, and read that section. Make certain you have the correct indicated memory card. Then, look at the index and find, Formatting Memory Card; it's VERY simple and may only take a few seconds, only requiring you press down on 2 buttons.

Look, as I tell all newbies, READ the Camera's Instruction Manual; you don't have to study it and memorize anything but do familiarize yourself with functions and features and options, and what they are and where to find them for a more rewarding photography experience that will yield you much better photos. Read a few pages every night before going to sleep, or while you in front of the TV watching a program or show (read during the commercial ads; who watches and pays attention to commercial ads?).

Go to the camera settings and you'll find option for formatting the card.