Firstly, you do not need to create a completely new repo to reorganize your projects.
Secondly, if you can, look at the fullness of your solution repository and create and svn add branches, tags, trunk folders. DO NOT CHECK them; you will svn move each other folder (project folders) in trunk , and then do it all in one go.
To illustrate, I created a SampleRepo , checked it, then svn add ed and svn commit dragged several placeholder project folders:

Then I created the branch tags, tags, and trunk at the root of the repo check, then svn add ed them using TortoiseSVN:

Repo check now looks like this:

Now I select all the project folders and drag them into the trunk folder, selecting SVN Move versioned () here :

The root of the SampleRepo folder now contains only branch tags , tags, and trunk . If you right-click on any space in the SampleRepo folder and select TortoiseSVN -> SVN Check for Changes , you should see something like this

Finally, I right-clicked any spaces in the SampleRepo folder and select TortoiseSVN -> SVN Commit ... , add a commit message and click OK .
Now, if I right-click on any space in the folder SampleRepo -> TortoiseSVN -> SVN Show Log , I will see this

Done!
NB: The reason I asked for a full repo check is because then you can minimize the number of commits that you will need to make in order to achieve the desired restructuring. You can perform server-side restructuring using the TortoiseSVN Repo Browser, but then you will need to move each folder one at a time.
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