I think you are of by a few magnitudes as this is only 1 square kilometer? The largest solar park in India is 56 square kilometers in area (or 10 million solar panels which are at least(?) 2 square meters in size).
Installed solar grew by around 130GW in 2020 according to this https://www.iea.org/reports/solar-pv which implies somewhere on the order of a billion square meters so you're out by a factor of at least 1000
and there about 20TW of electricity production to replace. So we need 120x 2020's output to replace electricity.
Other uses of fuels are about an order of magnitude more
So the delta is about 100-1000 given a decade of production. Less if we start to reign in the gratuitous waste of the west.
The output of your calculation is a testament to how grossly inefficient corn ethanol is. Not an endorsement of it.
Assuming your initial numbers are correct, the approx 1e10 should be 1e7 (rounding down from 4.5e7), as 1 million sqm equals 1 sqkm (this is different from 1 kilo square meter; see cube square law etc.)
You also do not take into account that solar panels have an expected lifetime of over 20 years - your current calculation seems to want a panel produced every year for every field.
Taking these into account brings the production defecit factor down to ~ 1e5, which is still unfathomably huge but at least marginally more achievable than the 1e9 answer you got.
The global production of solar panels was 180 GW in 2020. Assuming around 200 W per square meter, you get 1 billion square meters of solar panels. So their initial number is off by a factor of 1000.
It is also nonsense.
But even using the figure from a sibling reply, 1e5: so what? There is no need to put solar panels on every square km of farmland, or even on the 1/10th of it needed to fix the same calories; nor any value in trying or discussing trying.
If civilization does not collapse immediately, or even somewhat later, we will have centuries to build out solar. Future panels will last longer than today's, and be more efficient, and cheaper and lighter. Production, transport, and deployment will be increasingly automated. Today's production rate is not any kind of limit, and panels built today will not anyway evaporate next year. Build-out is cumulative.
Meanwhile, the nutritionally most valuable crops will not be displaced. Only cereal grains fed to animals are legitimate targets.
Furthermore, as I noted originally, panels placed in crop land will not displace crops, but coexist with them.
Global farmland is about 45 million square kilometers, approx 1e10 more.
Lets say the solar panels cover 10% of the field. That 10% produces 10x as much, so you've approximately doubled your fields overall productivity. We're currently a factor of 1e9 short of producing enough to do so (and it's not like PV cells are not currently produced at scale).
1e9 is an unfathomably large delta. We'd be converting most of the planet into PV factories & mines to supply them.