Will a signed letter from Hospice of Lansing, with the stated $7720.00, value of our donation of 4 cemetary lots suffice instead of an appraisal?

Unfortunately, a letter from the charity may not meet the IRS guidelines, unless a qualified appraiser provided the value quoted in the letter.

According to IRS Pub 561, if you claim a deduction for a contribution of noncash property worth more than $5,000, you will need a qualified appraisal of the noncash property and must fill out Form 8283, Section B. Generally, you do not need to attach the qualified appraisal itself, but you should keep a copy as long as it may be relevant under the tax law.

There are some exceptions to this requirement, but cemetery lots are not on the list.