The translation from Japanese to English is not good. I think that you are asking how to combine several projects into one. This is the answer for that.
If 2 projects involved...
You export the Timeline from project 1 to a file saved to the computer hard drive.
Then you import that export into project 2.
If more than more than 2 projects involved...(example 4)
You export the Timeline content from each of your projects (1, 2, 3, 4) to a file saved to the computer hard drive.
Then you import the export files (File 1, 2, 3, 4) into a new project 5 for the final export.
The format of the exports should be consistent with your project settings. You cannot import a project file (.prel) into another.
So, you will have to export each of the Timelines using one of the sharing choices.
Please let us know if the information above is what you were looking for.
If you need more information, please let us know what version of Premiere Elements that you are using and on what computer operating system it is