See the official gitbook: https://soroban-react.gitbook.io/index/ .
import { useContractValue} from '@soroban-react/contracts'
import { useSorobanReact } from '@soroban-react/core'
const balance = useContractValue({
contractId: Constants.TokenId,
method: 'balance',
params: [contractIdentifier(Buffer.from(Constants.CrowdfundId, 'hex'))],
sorobanContext: sorobanContext
})