The htdocs folder is not that important, it contains (mostly) the wordpress scripts, which can easily be retrieved by a new installation. BUT: some contents like Pictures are stored in an Upload Folder, these are lost, if you dont have a backup.
By far most important is the MySQL data folder, as it contains all MySQL Databases und WordPress puts all contents (all your menus, your sites etc.pp.) into MySQL Databases. If you have a backup of that data folder, everything should be fine. If you dont have a backup, it is a disaster. There is no way to retrieve that data without having a backup.
Images in the 'Uploads' folder is a problem as the WordPress installation does not recognize the new copied images.
Exactly as i told above.
Where is the data of all my pages and posts so I can copy them over, or is this not possible
See above, your data had been stored in MySQL Databases, which are placed in the data folder of MySQL (i.e. c:/xampp/mysql/data). If you deleted this folder, there is no way back.
I have a backup of the whole folder including the installation of a site I am developing in Wordpress.
Of which "whole folder"? If you have a backup of c:/xampp, everything is fine, If you only have a backup of the htdocs folder and or the wordpress folder, nothing is fine.
If you have a copy of the MySQL data folder, stop Apache and MySQL, rename the original data folder to somewhat else (for example rename it to data-original), then copy the whole "old" data folder from your backup to the the Xampp installation. If you are lucky, this already restores all your WordPress data and links (for the uploaded pictures etc.).