I wanna know that is there any platform where after depositing BitcoinBTC it can be automatically converted to on others currency (specially in stable coin).
All popular exchanges, like Binance, Kraken, Coinbase do provide this option for merchants, but fees vary and I'd suggest you do a good-read of the terms and conditions. Additionally, there is BitPay that, if I'm not mistaken, does have that option too.
If you consider keeping the bitcoin, and converting it manually to another currency, check out
BTC Pay server, which is an open-source, self-custodial alternative.
You wanna start accepting BTC but then you wanted to turn it into stablecoin after, that seems pointless. Why not just accept stablecoin directly?
It shouldn't be taken for granted that customers have stablecoins.