According to the specifications I found, the LG MS210 supports 3GP, 3G2, MP4, and WebM formats. You need a video editor that will work with those formats and the format you used in particular.
First make a couple of copies of your video and store them in different locations.
Then pick a computer or other device that you are willing to "risk" to some extent by installing video editing software.
Go online and look for video editing software - something free or perhaps a trial version that may be limited in scope. But still have the rotational editing ability you that you need. I.e., 90 degree rotation or portrait to landscape. The software should also be capable of working with/editing the format of yiour video.
Then try some...