There’s plenty of blog and forum posts on this so here’s one more. :)
On Windows this blog post is the way to go. It uses Win32DiskImager to create an image of the smaller micro SD to the Windows machine, and then put that onto the new larger micro SD.
I am on Linux, so I put in the existing micro SD card into the laptop and made an image of it to the laptop:
dd if=/dev/sda of=./pi.img bs=1M
/dev/sda with whatever is assigned to the micro SD when you pop it into your machine.
This takes a while and there’s no output. Once it finishes remove the micro SD, put in the new micro SD, and run the command in opposite:
dd of=/dev/sda if=./pi.img bs=1M
When that finishes, put in the new micro SD in the Pi, reboot, login and launch
sudo raspi-config, go to “7 Advanced Options” and “A1 Expand Filesystem”. Then reboot when prompted. That’s all!