How many Axis troops fought on D-Day, I've tried many sources and they have focused primarily on the Allied Forces.
According to this US Military Academy map of Normandy Operations June 6-12, 1944 the German divisions actually on or just behind the Normandy beach area on June 6 are as follows (West to East):
According to this source the nominal infantry strength of a German Infantry Division in the 1943-45 time period comprised:
This was supplemented by additional staff and support troops for each division. Grenadier battalions possessed firstname.lastname@example.org cm anti-tank guns, 36@panzerschrecks, and numerous mortars of various sizes included in the manning above. Ball park something in the neighbourhood of 8,000 to 10,000 men per division.
The Panzer Regiment at that time was similar in structure, with two Grenadier regiments replaced by Panzer Grenadier (motorized) regiments, and the third regiment replaced by a Panzer (armoured) regiment. This would supply roughly 2/3 the infantry strength of an infantry regiment, supported by two Panzer battalions (nominally ~50 tanks each) and a reconnaissance battalion in addition to the integrated engineer, artillery, anti-tank and other support troops.
In total this puts the total (nominal) field strength of the Axis units engaged on June 6, 1944 at roughly 35,000 riflemen/pioneers (5@6,000 + 1@4,500), 100 tanks plus supporting artillery, anti-tank and staff units.
As also noted by the map, this force is increased over the following 6 days by the arrival of these additional units:
Updated for major artillery components and estimates for Fusilier and Pioneer battalions.