How to download imessages onto a PC?

You can do this by using a third party application. I have seen this one get some good reviews here in ASC. It is called iMazing.

https://imazing.com/guides/how-to-save-iphone-text-messages-sms-and-imessages-to-your-computer

There are other apps that will do this. Search using “transfer iMessages to PC” without the quotation marks and you will see others that you can check out.

HI JRSailor51,

Welcome to Apple Support Communities. We understand that you'd like to move your Messages from your iPhone to a PC. We'd like to work with you on this.

While there are ways to share your Messages through iCloud with other devices, a PC is not one of the devices that this can work with. This resource will provide you with information on which devices work and how to set that up: Use Messages in iCloud - Apple Support

Even if you use iCloud for Windows, Messages is not a feature that can be shared this way: What is iCloud for Windows? - Apple Support

Here are the iCloud features available in iCloud for Windows:

1. iCloud Photos and Shared Albums

iCloud Photos automatically and securely stores all your photos and videos, and keeps them up to date on all your devices and on iCloud.com. Learn how to view photos and videos.

Shared Albums lets you share photos and videos with just the people you choose. They can add comments and share photos and videos with you. Learn how to create and share albums.

2. iCloud Drive

Securely store and organize your files in iCloud Drive. Access files and folders in File Explorer and share them with a link. Changes stay up to date on all your devices. Learn what you can do with files and folders.

3. Mail, Contacts, and Calendar

Access your iCloud Mail, Contacts, and Calendar in Microsoft Outlook. When you make a change on your Windows computer, your information is updated everywhere. Learn how to set up iCloud Mail, Contacts, and Calendar.

4. iCloud Passwords

iCloud Passwords can autofill your passwords in a web browser on your Windows computer. You can also manage your passwords in the iCloud Passwords app. Learn what you can do with iCloud Passwords.

4. iCloud Bookmarks

View your web bookmarks in a browser on your Windows computer. Learn how to set up iCloud Bookmarks.

If you're looking to move only a small percentage of messages, you may want to screenshot what you need and send it to yourself on your PC.

Take care!

I use and recommend the application TouchCopy which works both on Macs and PCs.

https://www.wideanglesoftware.com/touchcopy/