It appears that the qConsolidate has not been updated for Qgis 3.0. Are there any alternative plugins/functions available for exporting all layers and saving the project to a new folder?
QPackage plugin is very similar alternative to qConsolidate plugin in QGIS 3.
Qpackage is a tool to save both your QGIS project and data contained in the project to a new directory.
It allows to convert any GIS vector format towards the .shp only. You may also apply a new projection.
EDIT: QConsolidate3 plugin, modified version of QConsolidate, for QGIS 3 has been released.