Thanks to all the posts I discovered easily how to export to bitmap and save as png. However, the auto transparent background is not working properly. There are 3 objects in the file and only 2 appear with a transparent background. One of the lines is showing a white background around it. Any help on fixing this issue would be much obliged!

Welcome to InkscapeForum!

How did the objects come to be in the file? Did you draw them, or import them, or paste them in? Importing or pasting a raster image into Inkscape doesn't automagically convert it to vector. Or do you happen to use a Mac? Even if you drew the object, did you later copy/paste? There's a bug in Inkscape for Mac users, where pasting an image causes it to become rasterized (no longer vector). The background that you describe indicates that it may not be a vector object. You can avoid it by using Duplicate, rather then Copy/Paste.

If none of that info seems to apply to your file, we might need to look at the SVG file, to know for sure.