I want to update my SVN-Project before I start the build-procces. I need to reach this goal through the windows command line. Unfortunately I cannot find the command. Can you help me?
It appears that you want to run the svn update command, but you don't have svn.exe on your computer.
You need to install the Subversion client and make sure that it was added to the %PATH% environment variable. If you are on Windows, you can grab the latest command line tools from https://www.visualsvn.com/downloads/.
If by some reason you still cannot run the svn.exe command line client, you need to specify what's happening on your side in your question and give more details & context.