convert a dmp into a sql file

Is that practicable?

you can extract the DDL from a dmp file into SQL statements through the use of the SHOW=y option in the imp command. as far as the individual data inside the tables the answer is no.

in that case, how the appropriate command is?

The command is (along with whatever import params you want):

imp show=y file=filename.dmp

i put this in the command line

imp 'system/sample2@sample as sysdba' show=y file=sample.dmp full=y

and everything it worked properly.

The problem is if i could store allk these sql statements in a sql file.

Have you tried this :
imp 'system/sample2@sample as sysdba' show=y file=sample.dmp full=y > yourFile.sql

the generated sql file is always null :(

Specify INDEXFILE = file.sql in your IMP command to get the script file.

everything worked fine, but is there any good utility to convert the file into a mysql dump file?

http://www.kiyoinc.com/nxtract.html