Let's do some calculation for a fictional solo miner. According to current total Bitcoin mining network hash power, see
https://mempool.space/mining, all miners execute on average a total of roughly ~600EH/s (exahashes per second, that are 630x10
18 hashes per second) to mine a block on average every 10min.
Let's assume our fictional single miner (solo miner) has ten Bitmain Antminer S21 ASICs, each capable to deliver (as advertised by Bitmain) around 200TH/s (terahashes per second, ie. 200x10
12 hashes per second), all ten ASICs together deliver at best 2 PH/s.
Now, what's the probability for our fictional miner to find a valid block at current difficulty? Divide his hash power by current total hash power: 2 PH/s / 600 EH/s equals 1/300,000 (in decimal that's 0.000003333..., this isn't exactly a high probability to hit a block in favour of the rest of the mining network).
If you need percentages for understanding: with the total network's chance is on average 100% to find on average a block every 10min with roughly 600EH/s, our fictional solo miner's chance is only 0.0003333...% per block on average. If you only have one ASIC of above (which is already high-end) your chance is ten times less...
Bear in mind: mining is a totally random process. You could find a valid block in the next minutes or you won't find a block as solo miner in the next year(s), depending on your own total hash power. We can only calculate statistical probability to hit a valid block on average.