I was using
Microsoft Windows 7 and I had installed
MikTex. Both were installed according to the instructions given in this
Ĺink. I developed a document there and now I am on
Ubuntu 12.04LTEand I installed
TeXStudio but could not find
Ubuntu. So I installed
TexLive. When I try to compile my previously developed document, it gives error. It is missing many
.styfiles. I tried to manually add sty files but actually it is hectic to add all the files. I have very long document and it was working fine in windows. Please help!
I was using
The Linux version of MiKTeX was always declared as provisional, and is meanwhile not anymore available for download from MiKTeX.org. Therefore you are forced anyhow to use TeX Live, but apparently you used the pre-installed version of Ubuntu. For this issue we have a good Q & A here on TeX.SX: How to install "vanilla" TeXLive on Debian or Ubuntu? (and judging from comments this seems indeed to have helped you).
But apart from this there is still a number of packages, where MiKTeX is more liberal in estimation, what is called free. For several fonts of this type you can execute the script
getnonfreefonts, that is included in TeX Live. For other packages, maybe also some fonts, there is no other solution then to manually install them. You can read for this these questions and answers: Where do I place my own .sty or .cls files, to make them available to all my .tex files? and especially for fonts Manual font installation.
Regarding TeXstudio: This is a multi-platform program, there is a version for Linux as well as one for Windows.
At least Fedora did split up TeXlive into literally hundreds of packages, mostly containing a single LaTeX package or it's documentation. What is installed by default is a somewhat minimalistic set. Missing
.sty is somewhat common, the solution is to ask to install the package, here through names like
tex(dcolumn) for the dcolumn package. Presumably Ubuntu has similar tools that allow you to install exactly what you need.