המחשב שלי התקלקל ופורמאט .יש לי פרמייר 2018 משולם עם מספר סידורי. לא מצליח להגיע להפעלה ולהורדה מחדש

Please ensure your computer meets or exceeds the minimum system requirements to run the latest Creative Cloud + OS + all other apps you use. Check each one below.
- https://helpx.adobe.com/creative-cloud/system-requirements.html
- https://helpx.adobe.com/premiere-pro/system-requirements.html

Owing to Adobe's version policy, the current version (2021) + 1 previous version (2020), there is no longer a 2018 download in CC Desktop App.  

The 2018 version does NOT have a serial number.  You need a paid Creative Cloud subscription which is activated by your Adobe ID and password, not a product serial number. 

If I misunderstood your question, please post back with more details.

i assume you mean premiere elements 2018. if so, you'll need your serial number, a compatible os, and the installation file here, Adobe Photoshop Elements 2018 Direct Download Links + Premiere | ProDesignTools

follow the directions (esp, step 1)

save the install file. it won't remain online.

thank jim @ prodesigntools.com