You cannot copy & paste the Simulink model to another document and keep the functionality of the Simulink blocks. Instead, you need to convert it to an image file.
For MATLAB R2019a and earlier releases: In Simulink, go to top menu bar and select "Edit -> Copy Model To Clipboard", and then paste it into other document.
For MATLAB R2019b and later releases: In Simulink, go to top menu bar and select "Format -> Screenshot", and then paste it into other document.
Alternatively, for any release, you can press "ALT - Print Screen" or use a third-party snipping tool to capture the Simulink model and paste it to other document.
If you only need a part of the model, the solution is to copy and paste the blocks you highlighted into a new Simulink file and convert it into an image using the methods described above.
