The exponent $(\ast )$ in $0.00700000\times {10}^{\ast }=7.00000$ is

$\underset{–}{\text{Need to find:}}$ The exponent $(\ast )$ in $0.00700000\times {10}^{\ast }=7.00000$

$\bullet$ Multiplying by $10={10}^1$: Decimal point moves $1$ unit to the right, i.e.,
$0.00700000\times 10=00.0700000=0.0700000$

$\bullet$ Multiplying by $100={10}^2$: Decimal point moves $2$ units to the right, i.e.,
$0.00700000\times 100=000.700000=0.700000$

$\bullet$ Multiplying by $1,000={10}^3$: Decimal point moves $3$ units to the right, i.e.,
$\underset{–}{0.00700000\times 1,000=0007.00000=7.00000}$

$\therefore 0.00700000\times 1,000=\underset{–}{0.00700000\times {10}^3=7.00000}$

Hence, the exponent $(\ast )$ in $0.00700000\times {10}^{\ast }=7.00000$ is $\underset{–}{3}$.