how do i revert ntfs file system back from ext3?

i was trying to install ubuntu and i did something to my drives

If you installed "alongside", allowing the Ubuntu installer to shrink the Win7 OS partition to make room, it's very likely you corrupted the Windows filesystem in the process -- because the installer will not prevent you from shrinking the partition too much. Whereas, if you had used the Win7 Disk Management utility to do the shrinkage, it would have prevented that same problem.

If you corrupt the Windows filesystem, it won't boot anymore -- which seems to be what is happening.

If you chose the option to "user the entire disk", then the installer did what you told it to do -- reformatted the entire disk, erasing all the partitions and replacing them with Linux filesystem partitions. And, unless you used a very old version of Ubuntu, or manually changed the filesystem in use, the main partition would be Ext4, and there would be a small swap partition.

If you can still boot your PC into Ubuntu, then do so, open GParted and look at the set of partitions on the drive. IF all you see is Linux filesystem partitions, then Windows is GONE. However, if you see there are still NTFS partitions, then Windows is still there, just with a damaged boot loader.

You need to get back with what you find before getting further details on what to do.

I suspect that you will have real problems recovering from this incident.

I'm not sure about the latest Ubuntu installer, but the Linux Mint installer doesn't provide accurate explanations of what it will actually do.
I obliterated an external HDD (full of backup files) by choosing "Replace existing installation".
It replaced the existing installation and obliterated all of the other partitions on that drive.

Not that it help now, but in the future you should create a backup HDD/SSD image before attempting potentially damaging operations.

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I prefer to use Macrium Reflect.