There are two ways to do this; since they both have their merits, I'll include both of them.
1. The Project Manager
Open File → Project Manager. It's pretty straightforward, just select the sequences you want to export. If you want to clean up the preview files, uncheck Include Preview Files. Select the target directory and click ok. Repeat this for every sequence you want to export to an individual project. The problem with that approach is that this will also copy your media assets to the new project's directory, which you might not want.
2. Importing sequences
Another option is to import sequences from other Premiere project.
- Create a new project in Premiere.
- Select File → Import.... In the pop-up window, select your old project file that has all the sequences in it.
- Another dialogue window will pop up asking you whether you want to import the entire project or individual sequences. Select Import Selected Sequences.
- This will open another window where you can browse your old project and select the sequence(s) you want (to select multiple sequences, hold CTRL / CMD while selecting them).
This will not copy or move your media assets to a new directory. Instead it will just import the selected sequence(s) and all media assets it contains into your new project. This however will not import any assets that aren't used in your imported sequence(s). So if you're still working on one of the imported sequences in the new project and want to add clips you had already imported in the old project but hadn't used yet, you'll have to import those manually. To prevent that, import all media assets that are relevant to the sequence into your new project before importing the sequence and make sure Allow importing duplicate media is unchecked in the import dialogue.