If you needed help to install WordPress I recommend you do not use custom media folder.
Either stick to the Year/Month structure default, or put all your media in the wp-content/uploads folder (in Settings > Media > uncheck Organise my uploads into month- and year-based folders).
Most WP installations use less than 100 photos and other media. That is not too much to handle in one folder or in Year/Month structure.
Do not use the media library as a reservoir of unused photos you may “someday” use. That makes it unmanageable.
Instead upload the image(s) you want to use in each post/page as you need it. If you want to reuse images down the track you can find them via your pages or the media library.
Pro Tip: Use the Title, Alt text and Description fields in the media library to describe the picture so you can search for it by text. e.g. Photo of Jerry fishing on the lake.
Pro Top 2: Use the caption field to put your “photo credit” info and description e.g. PaulZag at work. Photo by Erica Massingham/Some Stock Library
If you absolutely insist on custom folders use https://wordpress.org/plugins/enhanced-media-library/