Ok so the two different collections you have are actually two different types of collections. The blog collection is a folder collection. Folder collections represent one or more files with the same format, fields, and configuration options, like authors, blog posts or products.
The pages collection is a file collection. Each item in a file collection has an explicitly set configuration, perfect for unique (mainly static) pages.
You could name your current files collection differently (like static), and make a new folder collection called ‘pages’. That way you’ll be able to create new entries from the CMS. You will have to adjust your front-end accordingly.