Need help about how to move content from Album to Genre

Hi guys, about 10 years ago when i started to make my library of music, at that time im using the ipod, somehow i think is very convenient for me if i im using the "album" instead of "genre" because of the display UI of the ipod at that time. Example : if this song genre is Rap, instead type rap in "genre" , im typing it to "album". Somehow its work for me, and im keep doing that till now (now i have about 900 songs), but now that kind of setup is not working anymore, and all i want to do is switch the content in "album" to "genre" for all my songs.
Im used to listen to music with 1 genre at a time, that the reason why im doing that stuff. And then i found out Mp3Tag is a great software to manage songs. But i dont know how to move the content from Album to Genre.
Can someone help me pls, thanks you guys alot.
P/s: sorry about my English, its not my main language.

See the FAQs.

Yeah with Mp3Tag, I just want to move the "album" part of all my songs to "genre".

So it is "copy" first (as described in the FAQs, only that you use GENRE as target field and ALBUM as source.
And then you use the tag panel to delete the contents of ALBUM.

Did i do something wrong ? The content in album just vanish.

Yes: if you copy (format) the contents (value) of the empty field GENRE to ALBUM then the field ALBUM becomes empty.
So the target field is GENRE and you supply the value from %album%

yeah thks alot, im just so noob, but now how do i use the tag panel to delete Album's content....

Select the files
In the tag panel, go to the field for ALBUM
Select <delete> from the drop-down list
Press Ctrl-S to save the changes.

Omg thks you alot, my life is saved.
Love this community <3