You should update minSdk with higher version. Follow this path to find build.gradle file. android>app>build.gradle. then update the minSdk with higher version

defaultConfig {
    applicationId = "com.example.project_name"
    minSdk = 29
    targetSdk = flutter.targetSdkVersion
    versionCode = flutter.versionCode
    versionName = flutter.versionName
}

For find latest sdk versions, use this link.