I've got a backup of my database in mysql of 250MB !!

How do i restore it inside a new database on another server ?

Or simply use phpMyAdmin for restore porpoise.

Using:

mysql -u USER -p -h HOST DATABASE < mysqldump.sql

You're supplying no detail on which operating-system you are on and what type of backup you've, however the short response is

mysql -u username -p -h hostname databasename < dumpfile.sql

where dumpfile.sql must be personal files that contains SQL claims, for instance created with mysqldump.