I just installed ubuntu but I cant find the files that I had on windows?
Ubuntu and Windows are different Operating system. The softwares that work on One operation system may or may not work on another operating system (OS).
Generally, If two OS can run and recognize same binary program/files, both of them can run that software. But, those files/programs need to be binary compatible. But, programs for Windows and Ubuntu's are not binari compatibles and hence they are different. So, You can't run your Windows programs on Ubuntu (except with the help of some emulation software such as WINE).
Even if You install another copy of Windows in another parititon in the same Computer, you will not find your installed programs (except the default programs automatically installed by Windows). Because, You have done installation in a new partition. Also, installing Windows again on the same drive will not help.
So, It is clear, If you install Ubuntu, you can't find the Windows programs in it. If you installed in another partition (other than Windows), You can still boot on Windows. If you installed Ubuntu on the same partition as Windows, You replaced Windows and you will never find those old Windows program.
See these links to get an idea about OSes, Difference between Windows and Ubuntu.
And also see these to get a general introduction to Ubuntu and Linux:
See these links to get help on Using both Windows and Ubuntu on the same computer: