Load the PDF into QGIS, deselect or remove all the layers your aren't interested in, leaving you with just the contours. You should end up with something like this (using Quick Map Services' OSM base map):
Note that the noise level of these contours is lost. Its an annotation in the PDF that has no geographic reference to the line, so does not load with the other layers from the PDF. So if you need the noise level for each line you need to add a new attribute to each contour line and enter it manually.
Vector: Geometry Tools: Extract Nodes to create a Point shapefile of the nodes of the contours. Note these points form the line segments that make the contour lines. If you need more points on the lines then you need to densify the lines first, which is another step.
Then with the point layer loaded, it should now look like this:
Vector: Geometry Tools: Export/Add Geometry Columns. Decide what coordinate system you want the points in. Don't click the "save to a new shapefile" box, we're going to add them to the current map layer. Hit OK, then when its run hit Close.
Now your attribute table should have the X and Y coordinates:
in this case in the original coordinate system.
Saving the shapefile will give you a DBF file that you can read into Excel or other spreadsheet program for further processing and upload to your database...