Yeah poor description... You also didn't said IF :1. You managed to start properly apache server? 2. "xampp dashboard"? You mean Xampp control panel?! 3. In order to have SOMETHING in htdocs YOU must put it there! Like you go online to the REAL wordpress and download that plugins.php file and put it in htdocs. "xampp dashboard" (i assume is control panel you want,...if not control panel you meant my bad) YOU CAN'T access htdocs from XAMPP Control Panel... htdocs as a folder is located on your drive in E.g. xampp\htdocs ..... or wherever you installed it XAMPP.... OR you access htdocs folder CONTENT via a browser (if you created something in there ofc like a folder armorgames.com or in your case wordpress)... Now since you mentioned "wordpress/wp-admin/plugins.php" THERE must be a folder inside htdocs that is named wordpress... inside that wordpress folder another folder named wp-admin.... and a file named plugins.php... (So basically you want to RECREATE the online version of wordpress i assume) BUT to recreate it LOCALLY you must follow the ORIGINAL folder structure.... If you didn't do that is IMPOSSIBLE to find what you look simply cuz doesn't exist.
ALSO to be able to access "localhost/wordpress/wp-admin/plugins.php" YOU must edit another file named "hosts" (disable network first) and add a line like this: 127.0.0.1 wordpress AND once you start apache server ...(This will instruct) type in what you want in a BROWSER: localhost/wordpress/wp-admin/plugins.php.... AND IF you have that folder hierarchy stated before you should access plugins.php.....
(I had once a similar problem!
That's why so detailed solution.... and this is LOW version of detail, you don't wanna know the FULL one