I have a 10 year old MacBook Pro and will buy a new one soon. 1) What cable do I need to connect the computers together so I can move software and my documents from the old laptop to the new?

What is the date of your most recent backup, and by what method?

You can generally copy your files off the backup. Migration Assistant can make it easy. If you are ready-to-go when you first set up the new computer, that makes it really easy.

How to move your content to a new Mac - Apple Support

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Strictly speaking you do not need a cable. You can transfer information using your wireless network.

Transferring information can take a long time. It can be difficult to predict how long it will take to finish, and it's not easy to determine if your wireless connection is the limiting factor. Twelve hours into the migration you may be wishing you had connected the Macs to each other with a cable.

If you are fortunate enough to be in an area free from wireless interference, say in the middle of the Pacific Ocean, wireless will be perfectly ok:

There are no other wireless networks within miles of that example.

HWTech wrote:

For Target Disk Mode you will need to have a USB-C to USB-C Cable and a USB-C to Thunderbolt 2 Adapter (assuming the older laptop has a Thunderbolt port).

Actually I made a mistake. Instead of the USB-C to USB-C Cable you would need a Thunderbolt to Thunderbolt cable. Sorry for the confusion.

For Target Disk Mode you will need to have a USB-C to USB-C Cable and a USB-C to Thunderbolt 2 Adapter (assuming the older laptop has a Thunderbolt port).