set aStr to "126　ひよこ豆コーヒー豆だだちゃ豆"
set n1Res to filterNumStr(aStr) of me
log result
–>　　"126"

set aStr to "ひよこ豆コーヒー豆だだちゃ豆 345"
set n2Res to filterNumStr(aStr) of me
log result
–>　　"345

set aStr to "ひよこ豆コーヒー豆999だだちゃ豆"
set n3Res to filterNumStr(aStr) of me
log result
–>　　999

on filterNumStr(aStr as string)
　　set aLen to length of aStr
　　set regStr to "＼＼d{1," & (aLen as string) & "}"
　　set aRes to findStrByPattern(aStr, regStr) of me
　　return aRes as {boolean, number}
end filterNumStr

on findStrByPattern(aText as string, regStr as string)
　　set anNSString to current application’s NSString’s stringWithString:aText
　　set aRange to anNSString’s rangeOfString:regStr options:(current application’s NSRegularExpressionSearch)
　　if aRange = {location:0, length:0} then return ""
　　set bStr to anNSString’s substringWithRange:aRange
　　return bStr as string
end findStrByPattern