、。
Dr. Kimura told me you're the leading authority in this field.
Literal
Kimura-doctor [from-から], you [subject-が] this [possessive-の] field [possessive-の] number-one-person is [quotative-と] humbly-heard-伺う.
伺う is humble keigo (kenjōgo) for 聞く ('to hear / to ask'). Using it to describe the speaker's own act of receiving information lowers the speaker relative to the (absent) Dr. Kimura. 第一人者 ('the number-one person, the foremost expert') is a Sino-Japanese fixed expression for 'leading authority.' から marks the source of the heard information.