Mississippi has a cost of living index of 84 relative to the US average of 100. This is significantly below average, making Mississippi one of the more affordable FIRE destinations. Your portfolio goes further here than in most states.
The 4% safe withdrawal rule suggests a FIRE number of 25x annual expenses. At Mississippi's median income of $46,500, that is $1,162,500. However, if you plan to spend more (or less) than median income in retirement, scale the number accordingly.
Mississippi taxes income at 0%–5%. In FIRE, your primary income comes from portfolio withdrawals, dividends, and capital gains. Long-term capital gains in MS are taxed at the same rate as ordinary income (but retirement distributions may have different treatment). Factor this into your withdrawal rate planning.