Dear Mohamed
you should convert your shapefiles into raster first and then convert the rasters into ASCII. You have to make your mind about which attribute of the shapefile you will base your raster on. For instance if you are looking to include the soil pH in your maxent model then you have to produce a raster of that shape file with the pH field being assigned as the value. Also you need to specify the cell size, snapping raster and the processing extent in the environments values in arcmap as to match those of your other ASCII grids that you are using along in Maxent to avoid any error message specifying un matched extents in the predictor layers.
Regards
Husam El Alqamy
Sr. Biodiversity GIS Analyst
Environment Agency - Abu Dhabi