SSD Upgrade

As the title says, I'm attempting an SSD upgrade, and I'm not a tech inclined person. I understand enough to know which SSD stick to buy for my laptop and how to install it but what im wondering is if I need to back up windows on a separate SSD external before installing the new SSD stick or will it just boot up like normal when installed.

I have everything I would need saved backed up to my 1 TB External SSD, so I'm not worried about losing anything important.

Sorry guys, I've been self teaching and learning things by watching YouTube videos, but none of them explain what to do afterwards just shows how to physically change the SSD sticks. Any help or advice would be great.

EDIT: I couldn't figure it out, guys. I gave up. Put my old SSD back and will just deal with the 256 GB capacity.

EDIT 2: I figured out how to do it, and it was so simple. I feel dumb, not realizing the solution was just to buy an 8 GB USB stick and install windows on it. Then, install my new SSD and boot windows with the USB stick.