If working with a PC, you’ll need to install the most recent version of Apple iTunes - as it is this that can be used to transfer photos from PC to your iPad.
Whilst you’ll be able to transfer photos, you’ll not be able to maintain your current file/folder structure. Photos will be imported into the iPad photo library.
If you are happy to forego use of the iPad’s native photo management, you might alternatively consider using a third-party file management App. In so doing, you’ll be able to manage and maintain your current file/folder structure on the iPad. Two Apps come readily to mind, the first of which I use myself (using the Pro version) to manage photo and and other files - with similar needs to yourself:
File Browser - Document Manager (recommended for your stated needs):
https://apps.apple.com/gb/app/filebrowser-document-manager/id364738545
FE File Explorer: File Manager:
https://apps.apple.com/gb/app/fe-file-explorer-file-manager/id510282524
Both of the above have the equivalent “Pro” versions. If considering either, you’d be well advised to check which version is more suitable for your needs before purchasing.
You’ll still need to consider the method of transferring files between PC and iPad. You’ll be able to use Apple iTunes on your PC, a cloud service, or FTP/NFS. Reading the support information of the chosen App will likely help with your choice of methods.