Hi RileyAitkenhead,
welcome to the Apple (user-to-user) Community
Am no expert in this area, yet your request surely deserves a response.
Fortunately Apple Support has articles online that may help guide you:
Re: "Mac OS App Store Not Signing In"
"whenever i go to sign in with my apple id it says incorrect password"
You may need to access your Apple ID account online, and check or correct the password is up-to-date there.
Where to sign in to your Apple ID account online:
appleid.apple.com
If you forgot your password, and / or Apple ID:
https://iforgot.apple.com/password/verify/appleid
You may also need to be signed in (to your device) with your Apple ID
Sign in with your Apple ID - Apple Support
After you've signed in on a device with your Apple ID, that device should appear in the Apple ID list: Check your Apple ID device list to find where you've signed in – Apple Support
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Re: "i now want to update it to monery or Big Sur using the app store"
Apple support's article:
How to: Identify your MacBook Air model – Apple Support
says the newest compatible operating system for MacBook Air (2017) is macOS Monterey, so that's all good.
However upgrading from Yosemite to Big Sur or Monterey means changing all apps from 32 bit apps to 64 bit apps . . .
ie: Non-Apple (third-party) 32 bit apps will need deleting or upgrading.
Also, the upgrade should be done gradually. Rather than in one giant leap, the upgrade would generally need to be done in smaller steps.
About the transition to 64-bit technology and how it affects 32-bit apps:
32-bit app compatibility with macOS High Sierra 10.13.4 and later - Apple Support
macOS Mojave was the last version of macOS to run 32-bit apps.
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Where to find older MacOS updates:
How to download macOS - Apple Support
Trouble-shooting:
What to do: If you can't download or update apps on your Mac - Apple Support
If needed:
There are "Get Support" details at the bottom of this webpage:
MacBook Air - Official Apple Support
App Store Support also has a website online:
App Store - Official Apple Support
All the best :-)